1. Field of the Invention
This invention relates to a micro fluidic device comprising a valve/pump-unit. The micro fluidic device comprising said valve/pump-unit according to the present invention is preferably used in molecular diagnostics.
2. Background Art
The biotechnology sector has directed substantial effort towards developing miniaturized fluid sample transport devices such as microfluidic devices, often termed labs-on-a-chip (LOC) or micro total analyses systems (microTAS), for sample manipulation and analysis. These systems are used for detection and analyses of specific bio-molecules, such as DNA and proteins.
In general micro-system devices contain fluidic, electrical and mechanical functions, comprising pumps, valves, mixers, heaters, and sensors such as optical-, magnetic- and/or electrical sensors. A typical molecular diagnostic assay includes process steps such as cell lyses, washing, amplification by PCR, and/or detection.
Integrated microfluidic devices need to combine a number of functions, like filtering, mixing, fluid actuation, heating, cooling and optical, electrical or magnetic detection, on a single template. Following a modular concept the different functions can be realised on separate functional substrates, like silicon or glass. The functions need to be assembled with a microfluidic channel system, which is typically made of plastic. With small channel geometries this way of integration becomes a very challenging process. The interfaces between the substrates and the channel plate need to be very smooth and accurate, and the channel geometries need to be reproducible, while the functional substrates should have a minimum footprint for cost efficiency. Especially with functions, which need a fluidic as well as an electric interface, the separation of the wet interface is critical. Bonding techniques must be compatible with the biochemical reagents and surface treatments present on the functional substrates.
US-A1 2003/0057391, incorporated by reference, discloses a low power integrated pumping and valving array which provides a revolutionary approach for performing pumping and valving operations in micro fabricated fluidic systems for applications such as medical diagnostic microchips. This approach integrates a lower power, high-pressure source with a polymer, ceramic, or metal plug enclosed within a micro channel, analogous to a micro syringe. When the pressure source is activated, the polymer plug slides within the micro channel, pumping the fluid on the opposite side of the plug without allowing fluid to leak around the plug. The plugs also can serve as micro valves.
However, the pump system of US-A1 2003/0057391 does not provide a sufficient small dead volume and does not provide an optimized fast fluid transport. Further, the plugs must have a positive fitting to avoid sample fluid leakage thus the low power integrated pumping and valving arrays can not be provided at low vertical range of manufacture.
US 2005/0098749 discloses a micro valve and a method of forming a diaphragm stop for a micro valve. The micro valve includes a first layer and a diaphragm member to control the flow of fluid through the micro valve. The method comprises the step of forming a contoured shaped recess extending inward from a surface of the layer by using a laser to remove material in a series of areas, at successively greater depths extending inward from said surface. Preferably, the recess has a dome shape, and may be formed by a direct-write laser operated via a computer aided drawing program running on a computer. For example, CAD artwork files, comprising a set of concentric polygons approximating circles, may be generated to create the dome structure. Modifying the offset step distance of the polygons and equating certain line widths to an equivalent laser tool definition can control the laser ablation depth. Preferably, the laser tool definition is combined with the CAD artwork, which defines a laser path such that the resulting geometry has no sharp edges that could cause the diaphragm of the valve to tear or rupture.
US 2005/0098749 is directed to a micro valve only. Thus, the micro valve unit of US 2005/0098749 does not simultaneously integrate a pump as well as a valve function in the same unit. Further, the diaphragm member is not flexible so that the micro valve unit of US 2005/0098749 does not form and reform a temporally channel through which a fluid flow can be directed. As disclosed in US 2005/0098749 the diaphragm member opens a hole at a specific gas pressure so that the gas can pass through. However, the gas can not be pumped with the diaphragm member.
In the last decade, considerable research efforts have been made to the development pump-systems for microfluidic system devices in order to reducing the analyze samples volumes of liquid.
Despite this effort, there is still a need for a valve/pump-unit with an optimized reduced dead volume.